Ectoprocts may have descended from a vermiform, burrow-dwelling lophophorate ancestor that would probably be classed with the Phoronida if it were living. Stripped of their adaptations for small size, coloniality, and skeletonization, ectoprocts closely resemble phoronids. We propose that ectoprocts probably arose from a lineage that became epi- faunal, reproducing asexually to form tangled aggregations on hard substrates. Under these circumstances the disadvantages of aggregation, chiefly related to crowding, were mitigated through the development of small body size and by adoption of colonial habit. Coloniality was favored because it regulated intraspecific competition by controlling dispersion patterns and the spacing of individuals. It permitted coordinated manipulation of the environment in feeding and waste disposal, enhanced protection, and provided the opportunity for functional differentiation among individuals, thus promoting efficiency. Miniaturization led to the loss of distinct circulatory and excretory systems, while coloniality and eventual skeletonization led to a vast morphological and therefore ecological potential for the group. These factors appear to underlie the important place gained by ectoprocts in many benthic communities from the early Paleozoic until the present time.
- Adaptive strategies
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics